Initial

resources/app/client/pixi/layers/grid/highlight.js

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+/**
+ * A special Graphics class which handles Grid layer highlighting
+ * @extends {PIXI.Graphics}
+ */
+class GridHighlight extends PIXI.Graphics {
+  constructor(name, ...args) {
+    super(...args);
+
+    /**
+     * Track the Grid Highlight name
+     * @type {string}
+     */
+    this.name = name;
+
+    /**
+     * Track distinct positions which have already been highlighted
+     * @type {Set}
+     */
+    this.positions = new Set();
+  }
+
+  /* -------------------------------------------- */
+
+  /**
+   * Record a position that is highlighted and return whether or not it should be rendered
+   * @param {number} x    The x-coordinate to highlight
+   * @param {number} y    The y-coordinate to highlight
+   * @return {boolean}    Whether or not to draw the highlight for this location
+   */
+  highlight(x, y) {
+    let key = `${x},${y}`;
+    if ( this.positions.has(key) ) return false;
+    this.positions.add(key);
+    return true;
+  }
+
+  /* -------------------------------------------- */
+
+  /** @inheritdoc */
+  clear() {
+    this.positions = new Set();
+    return super.clear();
+  }
+
+
+  /* -------------------------------------------- */
+
+  /** @inheritdoc */
+  destroy(...args) {
+    delete canvas.interface.grid.highlightLayers[this.name];
+    return super.destroy(...args);
+  }
+}